The present invention relates to a wireless communication control technique and, more particularly, to a wireless communication control method, wireless communication system, and radio control station in a high-speed uplink packet transmission system.
In a third-generation mobile communication system including a mobile station, a base station, and a radio control station, a scheme using an uplink dedicated channel (DPCH: Dedicated Physical Channel) and an HSUPA (High Speed Uplink Packet Access) scheme as a high-speed uplink packet transmission scheme are available as schemes for transmitting data from a given mobile station to a base station in an uplink direction. These schemes are defined by the specifications (e.g., see 3GPP TS 25.211. v7.0.0. (2006-03) of 3 GPP (3rd Generation Partnership Project) serving as the third-generation mobile communication system international standardization project.
The DPCH is a dedicated physical channel which is made up from a DPCCH (Dedicated Physical Control Channel) which transmits a control signal and a DPDCH (Dedicated Physical Data Channel) which transmits data. A radio resource (indicating a base station reception power) is ensured for each mobile station in the radio control station. The data transmission rate can change depending on the uplink traffic and propagation environment. The transmission power is controlled in accordance with closed loop high-speed power control so as to make the reception quality of a base station constant.
On the other hand, the HSUPA scheme is made up from an E-DPCCH (Enhanced Dedicated Physical Control Channel) which transmits a control channel, an E-DPDCH (Enhanced Dedicated Physical Data Channel) which transmits data, and a DPCCH which transmits a pilot signal and a power control signal. The E-DPCCH and E-DPDCH are generically called an E-DPCH (Enhanced Dedicated Physical Channel). The radio resources are assigned to the interference and DPCH, and the remaining radio resources are used and scheduled between mobile stations at high speed, i.e., at an interval of 2 ms or 10 ms in the base station. The E-DPCH transmission power is controlled by adding a power offset determined by scheduling to the DPCCH transmission power based on the closed-loop high-speed power control.
When a mobile station transmits data to a base station using the DPCH or HSUPA scheme, the mobile station requests a radio control station to establish the DPCH (DPCCH in case of the HSUPA scheme). In this case, the radio control station performs AC (Admission Control) (e.g., see Harri Holma, Antti Toskala, W-CDMA FOR UMTS Revised Edition pp. 211-213, 2001). The AC is practiced using a cell load ρ given by:
                    ρ        =                              ∑            i                    ⁢                      (                                          SIR                i                                            SF                i                                      )                                              (        1        )            where SIRi (Signal to Interference Ratio) is the target reception quality of the DPCH established by a mobile station i and indicates a necessary SIR to satisfy a target error ratio, SFi (Spreading Factor) is the diffusion ratio of the DPCH established by the mobile station i and takes different values for different transmission rates, and Z is the total sum of all established DPCHs. When the HSUPA scheme is used, a DPCCH load is added. When the mobile station requests to establish a new DPCH, a cell load upon establishing the DPCH is estimated as in inequality (2). When the estimated cell load is smaller than a predetermined threshold value, a request for establishing a DPCH is permitted by
                                                        ∑              i                        ⁢                          (                                                SIR                  i                                                  SF                  i                                            )                                +                                    SIR              new                                      SF              new                                      <                  ρ                      max            ,            new            ,            UL                                              (        2        )            where SIRnew and SFnew are the SIR and SF of a new DPCH, respectively, and ρmax,new,UL is the AC threshold value. When the estimated cell load is equal to or larger than the predetermined threshold value, a DPCH establishment request is rejected. The AC threshold values are independently set for the DPCH and the DPCCH of the HSUPA scheme, respectively.
In the above third-generation mobile communication system, the AC regulates the DPCH in the radio control station. The base station measures the resource usages of the DPCH and HSUPA resources. The radio control station can know the RTWP (Received Total Wideband Power) representing the total reception power of the base station as the resource usage in the base station in accordance with a Common Measurement reported from the base station (e.g., see 3GPP TS 25.433, v 7.3.0. (2006 December)).
In the techniques relevant to the present invention, however, when independent wireless communication schemes are used in a mixed manner as in the DPCH scheme and the HSUPA scheme, and the resource used by one scheme (DPCH) increases, the resource usable by the other (HSUPA) decreases, thereby greatly degrading the throughput of the other (HSUPA) due to the following reason.
In case of DPCH and HSUPA, the resource usable by the HSUPA scheme is the rest of the resource used by the DPCH. Even if the remaining resource decreases, the radio control station cannot regulate the DPCH.